Safe infrared radiation-emitting apparatus

ABSTRACT

An apparatus for safely emitting infrared radiation, as when the radiation source must be separated from an article being irradiated. One surface of an infrared radiation-transmissive sheet or wall confronts the radiation source, and the opposed surface of the radiation-transmissive sheet or wall is cooled by a coolant transported thereacross. In one embodiment, a gasimpermeable, radiation-transmissive wall separates a combustion chamber housing a fuel-fired source of infrared radiation from an enclosure housing a conveyor carrying an article to be irradiated in the path of the radiation. A radiation mask having open and closed positions closes in response to stoppage of the conveyor to prevent radiation from entering the conveyor enclosure, and a sensor senses the integrity of the radiation-transmissive wall and halts the flow of fuel to the radiation source if the integrity of the wall is lost. An article in association with an inflammable solvent may thus be heated safely to remove the solvent by a fuel-fired source of infrared radiation.

Unite States Patent 191 Eichenlaub SAFE INFRARED RADIATION-EMITTINGAPPARATUS [76] Inventor: John E. Eichenlaub, 9321 Franklin Ave, West,Minneapolis, Minn. 55426 [22] Filed: Oct. 9, 1973 [21] Appl. No.:404,306

[52] US. Cl 432/185, 34/4, 432/194, 432/245 [51] Int. Cl. F27b 9/14,F27b 5/00 [58] Field of Search 432/173, 174, 175, 185, 432/188, 194,245; 34/4 [56] References Cited UNITED STATES PATENTS 3,150,864 9/1964Fetner et al. 432/175 X 3,542,349 11/1970 Ando et al. 432/185 PrimaryExaminer-John J. Camby Attorney, Agent, or Firm-H. Dale Palmatier; JamesR. Haller [4511 Nov. 19, M74

[5 7] ABSTRACT An apparatus for safely emitting infrared radiation, aswhen the radiation source must be separated from an article beingirradiated. One surface of an infrared radiation-transmissive sheet orwall confronts the radiation source, and the opposed surface of theradiationtransmissive sheet or wall is cooled by a coolant transportedthereacross. In one embodiment, a gasimpermeable, radiation-transmissivewall separates a combustion chamber housing a fuel-fired source ofinfrared radiation from an enclosure housing a conveyor carrying anarticle to be irradiated in the path of the radiation. A radiation maskhaving open and closed positions closes in response to stoppage of theconveyor to prevent radiation from entering the conveyor enclosure, anda sensor senses the integrity of the radiation-transmissive wall andhalts the flow of fuel to the radiation source if the integrity of thewall is lost. An article in association with an inflammable solvent maythus be heated safely to remove the solvent by a fuel-fired source ofinfrared radiation.

21 Claims, 2 Drawing Figures PATENIE mm 1 91974 m WN V m,

iii! i r BACKGROUND OF THE INVENTION Although fuel-fired heaters havelong been employed to heat homes and other buildings, such sources ofheat have not found great utility in the heating of articles containingflammable solvents, such as solvent-cast plastic sheets and the like.The recurring problem in such use of fuel-fired heaters is thepossibility that explosive mixtures of flammable solvent vapor and airmay be ignited by the fuel-f1red heater. Accordingly, those heaterswhich have employed a fuel-fired source of heat for drying flammablesolvent-containing articles have ordinarily required wide separation ofthe heat source from the article being dried. This has been accomplishedby having the heater heat air in a separate circulatory system, theheated air then being blown upon the articles to be dried. This system,it will be appreciated, requires a great deal of space for separation ofthe heat source from the solvent-containing articles and furtherrequires a great deal of expensive duct work and the like fortransporting heated air through a separate plenum from the heat sourceto the articles to be dried.

.BRIEF DESCRIPTION OF THE INVENTION The present invention provides anapparatus for safely emitting infrared radiation and which is useful inthe drying of flammable solvent-laden articles. The apparatus comprisesa source of infrared radiation, such as a gas-fired burner. An infraredtransmissive sheet or wall having a surface confronting the radiationsource is spaced from the source. The apparatus includes means fortransporting a coolant across the opposed surface of the wall to coolthe wall, whereby the radia-' tion source is isolated from the coolantby the radiation-transmissive wall.

In a preferred embodiment, a fuel-fired source of infrared radiation ishoused within a combustion chamber having a gas-tight infraredtransmissive wall spacedly confronting the infrared source and having anexhaust aperture permitting combustion product gases to be exhaustedfrom the chamber. The apparatus includes a conveyor for transporting anarticle to be irradiated exteriorly of the radiation-transmissive walland in the path of radiation emitted therethrough, an enclosure housingthe article during irradiation thereof, and means for transporting acoolant exteriorly of, but in cooling relationship to, theradiationtransmissive wall to cool the same. A mask havingradiation-transmissive wall, and means are provided for affectingclosure of the mask when movement of the conveyor ceases. A sensor isprovided for sensing the integrity of the radiation-transmissive wall,and is adapted to shut off the fuel supply to the radiation source whenintegrity of the wall has been lost.

DESCRIPTION OF THE DRAWING FIG. I is a side elevation view of theapparatus of the invention, shown in partial cross section and partiallybroken away; and

FIG. 2 is a broken away cross-sectional view of a por- DETAILEDDESCRIPTION OF THE INVENTION Referring to FIG. 1, the apparatus of theinvention designated generally as 10 includes a combustion chamber 12having an inclined upper wall 14, front and rear walls 16 and 18, and aradiation-transmissive lower wall 20. Front wall 16 has an aperture 16.1for supplying air to the combustion chamber, and rear wall 18 has anexhaust aperture 18.1 positioned adjacent the superior end of upper wall14 to exhaust combustion product gases from the combustion chamber. Airinlet aperture 16.1 may be provided with an adjustment (not shown) suchas a damper for regulating the amount of air which is permitted toenter. Housed within the combustion chamber is a source of infraredradiation such as a series of gas burners 20.1, which may be Schwanktype burners. Fuel, such as natural gas, is introduced under pressureinto a gas pipe 20.2 exteriorly of the combustion chamber, and the gasburners 20.1 depend from the gas tube 20.2 so that the gas burners aresubstantially aligned with one another in a horizontal plane, eachsubstantially equidistant from the radiation-transmissive lower wall 20of the chamber. Regulator valve 20.3 is provided exteriorly of thecombustion chamber for regulating the amount of fuel which is fed to theburners 20.1. The burners 20.1 include a ceramic element which, whenheated, emits infrared radiation. Each burner is provided with one ormore orifices (not shown.) through which air entering the chamberthrough aperture 16.1 may pass and be mixed with the fuel to form aflammable mixture which is burned at the bottom of the burners. Sincethe atmosphere within the combustion chamber 12 is not permitted tocontact an article to be irradiated, as will be explained more fullybelow, it is important from the standpoint of efficiency that a largeproportion of the energy resulting from combustion of the fuelbetransformed into infrared radiation emanating from the burners.

The inner surface of the combustion chamber may be made radiationreflective in whole or in part, as desired, so that a large proportionof the infrared radiation which is generated passes downwardly throughthe radiation-transmissive lower wall 20. The hot combus tion productgases will normally rise to the upper wall 14 which preferably, but notnecessarily, is inclined, and will then pass outwardly of the chamberthrough exhaust aperture 18.1 aided, if necessary, by means urging theflow of air through the chamber such as the powered exhaust stack 32.The upper wall 14 need not be inclined, of course, provided means aresupplied for otherwise exhausting the combustion chamber.

The radiation-transmissive lower wall 20 of the combustion chamber ispreferably a flexible plastic sheet which is supported about the lowerperiphery of the combustion chamber in a gas-tight manner to prevent theescape of combustion product gases through the lower wall from thechamber 12, and to prevent solvent vapors or the like emanating from anarticle being irradiated from passing upwardly through the lower wallinto the combustion chamber. The lower periphery of the combustionchamber may be provided with a connector 20.4 which forces the edges ofthe radiationtransmissive wall 20 sealingly up against the bottomsurface of a short, continuous flange 16.3 extending inwardly of thelower periphery of the chamber. The wall 20 may further be held in placeby means of bolts 16.2

' extending through the flange 16.3, the wall 20, and the connector20.4, as shown in FIG. 2. The radiationtransmissive wall 20 issufficiently flexible so that it tends to balloon downwardly slightly,as shown in FIG. 2, under the influence of a pressure differentialacross the wall, and ordinarily softens or melts below 1000F. Preferredmaterials for the radiation-transmissive wall 20 includepolytetrafluoroethylene (Teflon TFE, a trademarked product of E.I.DuPont DeNemours and Company, Inc.) which has an infrared transmissivityof approximately 0.88, poly(tetrafluoroethylene-hexafluoropropylene)(Teflon FEP, the DuPont Company) and a polyester such aspoly(ethyleneterephthalate), a product sold under the name Mylar by theDuPont Compony and which has an infrared transmissivity of approximately0.77. Unusually high temperatures may be tolerated by poly (4,4'-diaminophenylether pyromellitimide) (Kapton, a product of the DuPontCompany). Teflon TFE film having a thickness of approximately 0.002inches is preferred, since this material is flexible, is highlytransmi'ssive of infrared radiation, and is more resistent to hightemperatures than most other thermoplastic materials.

A conveyor 22 is provided beneath the radiationtransmissive wall 20 tocarry an article 24 into the path of infrared radiation emitted by theburners 20.1. For this purpose, a conveyor belt 22.] is trained aboutrollers 22.2 and 22.3 at opposite ends of the combustion chamber, thelast-mentioned roller being driven through a belt 22.4 which passes overand is driven by r rotating pulley 22.5. The latter is driven by anelectric motor (not shown) or the like which is housed within powerhousing 26. The conveyor belt is housed along at least a portion of itslength by an enclosure 28 having openings 28.1, 28.2 at either end. Theradiationtransmissive wall 20 forms a portion of the upper wall of theconveyor belt enclosure such that infrared radiation emitted downwardlyfrom the burners 20.1 is transmitted through the wall 20 to impinge uponthe article 24 carried by the belt. Articles to be irradiated may thusbe placed on the belt adjacent roller 22.2 and may be removed adjacentroller 22.3. The belt 22.1 itself is preferably of infraredradiation-transmissive material, such as Teflon TFE. A reflector 30 ispositioned beneath the belt in confronting relationship to the radiationemitted through the wall 20 so as to reflect infrared radiation upwardlyagainst portions of the articles 24 which are not exposed to thedownwardly directed radiation emitted by the burners, thereby permittingthe articles to be more uniformly irradiated and thus more uniformlyheated. Food products such as potato chips, cookies, and the like maythus be uniformly browned after having been baked by microwaves. Ifdesired, one or more of the surfaces of the conveyor belt may bereflectorized, or the bottom surface 28.3 of the enclosure may have anupwardly facing reflectorized surface. To avoid reducing reflectance byaccumulations of dirt and the like, however, a separate reflectorpositioned between the upper and lower runs of the conveyor belt 22.1,is preferred, as shown in FIG. 1.

Communicating with the combustion chamber through exhaust aperture 18.1and with the conveyor enclosure 28 through opening 28.2 is an exhauststack 32 having a powered blower 34 mounted at its upper gases from thecombustion chamber 12 and for simultaneously drawing air into theopening 28.1 in one end of the conveyor enclosure 28 and from opening28.2 in its other end. The air thus flowing through the conveyorenclosure is caused to pass across the lower surface of theradiation-transmissive wall to cool the wall. Baffles (not shown) orother means may be provided to insure that the air drawn through theconveyor enclosure passes sufficiently close to the bottom surface ofthe wall 20 so that sufficient heat is transferred from the wall to thecooling air to prevent the wall from becoming too hot so as to soften,melt, or otherwise become distorted. A damper 32.1 is rotatably mountedin the end. The blower is adapted to provide a partial vacuum within thestack 32 fordrawing combustion product exhaust stack 32 between its sidewalls to control the amounts of air issuing from the opening 28.2 in theconveyor enclosure. A second damper 32.2 is rotatably mounted betweenthe side walls in the exhaust stack adjacent the exhaust aperture 18.1leading from the combustion chamber to regulate the quantity ofcombustion product gases which are drawn through the exhaustlaperture.The dampers 32.1 and 32.2 may be joined by a chain 32.3, or may beotherwise connected, so as to rotate in unison, whereby the reduction inthe amount of air drawn from the conveyor enclosure results in a greaterquantity of combustion product gases being drawn through the exhaustaperture 18.1, and vice versa. The dampers 32.1 and 32.2 are normally soadjusted that a greater partial vacuum is drawn in the conveyorenclosure than in the combustion chamber, thus causing large quantitiesof cooling air to pass beneath the radiation-transmissive wall 20 andfurther causing the wall to balloon downwardly slightly as shown in FIG.2 under the influence of the pressure differential thus created betweenthe combustion chamber 12 and the conveyor enclosure 28. It may in somecases be desirable to provide air under pressure into the aperture 16.1in the combustion chamber and into the opening 28.1 at the front end ofthe conveyor enclosure, whereupon the blower 34 on top of the stack maybe eliminated. In this embodiment, the relative quantities of airintroduced through the aperture 16.1 and the opening 28.1 are such as tocause the pressure within the combustion chamber to be slightly higherthan the pressure within the conveyor enclosure, thus causing theradiation-transmissive wall to balloon outwardly slightly from thecombustion chamber. In any event, it will be understood that thepressure differential between the combustion chamber and the conveyorenclosure prevents flammable solvent vapors which may be produced in theenclosure from entering the combustion chamber.

A tension sensor 36 (FIG. 2) is mounted exteriorly of the combustionchamber and includes a downward projection 36.1 having a laterallyextending sensing finger 36.2, the end 36.3 of the finger being biasedgently upwardly against the outwardly ballooned radiationtransmissivewall 20. If the integrity of the wall 20 is lost (e.g., by rupturing ortearing or the like), the bal- 36 responds to very slight fluctuationsin the wall 20, so that small tears or rips occurring in the wall aredetected. Pinholes or extremely small tears in the wall, however, aretolerated by the sensing finger. It will further be understood that anyobstructions which develop which hinder the free flow of air through theconveyor enclosure or the combustion chamber will also be mirrored in achange in the pressure differential across the film, thus changingslightly the position of the outwardly ballooned wall which results inthe halting of gas flow to the burners 20.1. When softened by undulyhigh temperatures, moreover, the wall 20 will balloon outwardly to agreater degree, thus triggering the sensor 36.

A plurality of radiation opaque louvers 38 extend transversely in thecombustion chamber spaced closely above the radiation-transmissive wall20, and are rotatable about shafts 38.l journaled into the side walls ofthe combustion chamber. Simultaneous rotation of the shafts 38.1 causesthe louvers to move from a vertical position (solid lines in FlG. 1)which permits passage of radiation emitted from the burners, to a closedposition (shown in dashed lines in FIG. 1) wherein radiation isprevented from reaching the wall 20. One end of each louver shaft 38.1extends through the side wall of the combustion chamber, and anexterior, generally downwardly directed link 38.2 is rigidly mountedthereon. The bottom ends of the links 38.2 are in turn pivotallyconnected to an axially movable horizontal rod 38.3 such that axialmovement of the rod causes the louvers to move between open and closedpositions. The rearwardly extending end of the rod 38.3 enters the powerhousing 26 and therein is pivotally affixed to a rotatable link 26.1,rotation of which about its stationary pivotal connection 26.2 isgoverned through an appropriate controller 22.6 by rotation ornon-rotation of the pulley 22.5 driving the conveyor belt 22.1 as sensedby motion sensor 22.7. When the conveyor belt ceases to move, thecontroller urges rotatable link 26.1 to the right (as shown in dashedlines in FIG. 1), thus drawing the rod 38.3 to the right to cause thelouvers,

acting through connecting links 38.2, to assume a substantially flat,closed position. A purpose of the louver mechanism thus described is toprevent articles carried by the conveyor from becoming overexposed tothe radiation emitted through the wall 20 when the conveyor ismomentarily stopped. When movement of the conveyor is resumed, thelouvers are returned to their vertical position by the linkage elementsthus described. When in their flat, closed position, the temperature ofthe louvers themselves may become increased due to absorption ofinfrared radiation. When raised again to their vertical position uponresumption of conveyor movement, the heated louvers are thus positionedaway from the radiation-transmissive wall 20 so as not to causeoverheating, and possible rupture, of the wall. The louvers may beprovided with an infrared reflective surface to lessen the possibilityof overheating.

In another embodiment, the radiation-transmissive wall or sheet may bein the form of a circular drum into which wet clothes or other articlesto be dried may be placed, the combustion chamber extending in anannular fashion about the outer periphery of the radiationtransmissivewall and having fuel-fired sources of infrared radiation about thecircumference of the chamber and spaced from the wall. In thisembodiment, the the wet laundry is the coolant which is transported overthe inner surface of the wall 20 by rotation of the wall about its axis,or by internally mounted paddles, or the like. Since water isconsiderably more absorptive of infrared radiation than are mostfabrics, water from the wet laundry will be heated, vaporized, andexhausted through an appropriate exhaust stack which may also carry thecombustion product gases from the combustion chamber. The relatively lowinfrared absorptivity of the clothes prevents overheating of the clotheswhich might damage temperature sensitive fabrics. In contrast, gas-firedclothes dryers of the type in popular, present-day use either passcombustion product gases through the clothes for drying, or require aseparate plenum wherein air is heated and then passed through theclothes.

Manifestly, l have provided an apparatus for safely emitting infraredradiation in which articles to be irradiated are separated from theradiation source by an infrared radiation-transmissive wall having asurface which confronts the radiation source, the other surface of thewall being cooled by passage of a coolant thereacross. The wall providesa barrier to the communication of gases thereacross for reasons ofsafety and cleanliness. In preferred embodiments, the integrity of theinfrared radiation-transmissive wall is continuously sensed, and theradiation source is deactivated should integrity of the wall be lost. Amovable conveyor is pro vided for carrying articles in the path of theradiation emitted from the radiation source, and a mask is pro vided toprevent radiation from impinging upon articles to be irradiated when theconveyor ceases to move.

While I have described a preferred embodiment of the present invention,it should be understood that various changes, adaptations, andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:

1. Apparatus for safely emitting infrared radiation comprising a sourceof infrared radiation, an infrared radiation-transmissive, flexible wallsoftenable at a temperature below 1,000 F. and having a surface confronting the radiation source but spaced therefrom, means fortransporting a coolant across the opposed surface of the wall to coolthe latter, and means preventing access of the coolant to the radiationsource.

2. The apparatus of claim 1 wherein the radiation source is fuel-fired.

3. Apparatus for safely emitting infrared radiation comprising a firstchamber, a source of infrared radiation enclosed in the first chamber, asecond chamber adjacent the flrst chamber and desposed inradiationreceiving position with respect to the infrared radiationsource, an infrared radiation-transmissive flexible wall softenable at atemperature below l,000 F. and having one surface confronting theradiation source and an op posed surface confronting the second chamber,a coolant, and means for transporting the coolant across the opposedsurface of the wall to cool the wall.

4. The apparatus of claim 3 wherein the coolant includes an articleadapted to be heated within the second chamber by absorption of infraredradiation.

5. The apparatus of claim 3 including means for moving an article withinthe second chamber in a path permitting confrontation of the articlewith infrared radiation emitted from the infrared radiation source.

6. The apparatus of claim 3 wherein the source of infrared radiation isfuel-fired, and including means for -exhausting combustion product gasesfrom the first chamber.

7. The apparatus of claim 3 wherein the infrared radiation-transmissivewall forms a gas-tight wall of the first chamber confronting the secondchamber.

8. Apparatus for safely emitting infrared radiation comprising a firstchamber, a source of infrared radiation enclosed in the first chamber, asecond chamber adjacent the first chamber and disposed inradiationreceiving position with respect to the infrared radiationsource, an infrared radiation-transmissive gas-tight wall having onesurface confronting the radiation source and an opposed surfaceconfronting the second chamber, a coolant, means for transporting thecoolant across the opposed surface of the wall, and a sensor for sensingthe integrity of the infrared transmissive wall, the sensor including acontroller responsive to the sensor and adapted to deactivate theinfrared radiation source when non-integrity of the wall is sensed bythe sensor.

9. The apparatus of claim 8 wherein the infrared transmissive wall formsa common wall of the first and second chambers.

10. Apparatus for safely emitting infrared radiation comprising a firstchamber, a source of infrared radiation enclosed in the first chamber, asecond chamber adjacent the first chamber and disposed inradiationreceiving position with respect to the infrared radiationsource, means for moving an article within the second chamber in a pathpermitting confrontation of the article with infrared radiation emittedfrom the source, an infrared radiation-transmissive wall having onesurface confronting the radiation source and an opposed surfaceconfronting the second chamber, a coolant, means for transporting thecoolant across the opposed surface of the wall, a mask confronting thewall and having an infrared radiation-transmissive open position and aninfrared radiation opaque closed position, and including meansresponsive to the movement of an article within the second chamber andadapted to affect closure of the mask when the movement of the articleceases.

11. Apparatus for safely emitting infrared radiation comprising a firstchamber, a fuel-fired source of infrared radiation'enclosed in the firstchamber, a second chamber adjacent the first chamber and disposed inradiation-receiving position with respect to the infrared radiationsource, means for moving an article within the second chamber in a pathpermitting confrontation of the article with infrared radiation emittedfrom the source, an infrared radiation-transmissive wall having onesurface confronting the radiation source and an opposed surfaceconfronting the second chamber, a coolant, means for transporting thecoolant across the opposed surface of the wall to cool the wall, and anexhaust stack communicating with the first and second chambers forexhausting combustion product gases and coolant simultaneously from therespective chambers.

12. The apparatus according to claim 5 including an infrared radiationreflector in the second chamber and positioned to receive infraredradiation emitted from the infrared source and to reflect the sameagainst a portion of the article not confronting the infrared source.

13. Apparatus for safely irradiating an article with infrared radiationcomprising:

a fuel-fired source of infrared radiation;

a combustion chamber housing the infrared radiation source and having agas'tight, infrared radiationtransmissive flexible wall softenable at atempera- 5 ture below l,000 F. and spacedly confronting the infraredradiation source, the combustion chamber further having an exhaustaperture permitting combustion product gases to be exhausted from thechamber;

a conveyor for transporting an article exteriorly of the infraredradiation-transmissive wall and in the path of infrared radiationemitted therethrough;

an enclosure housing the article during movement thereof in the path ofthe infrared radiation; and

means for transporting a coolant exteriorly of, but in coolingrelationship to, the radiation-transmissive wall to cool the same.

14. The apparatus of claim 13 wherein the article enclosure ispositioned beneath the combustion chamber and wherein theradiation-transmissive wall of the chamber forms an upper wall of thearticle enclosure.

a conveyor for transporting an article exteriorly of the infraredradiation-transmissive wall and in the path of radiation emitted throughthe wall;

an enclosure housing the article during movement of the latter in thepath of the infrared radiation, said infrared radiation-transmissivelower wall of the combustion chamber forming an upper wall of thearticle enclosure;

a gaseous coolant; and

means for transporting the coolant comprising an exhaust stackcommunicating with the combustion chamber and with the article enclosureand adapted to simultaneously draw combustion product gases from thechamber and coolant gas from the enclosure, and to exhaust the same.

16. The apparatus of claim 15 including a sensor for sensing theintegrity of the radiation-transmissive wall and adapted to halt fuelfiow to the infrared radiation source in response to sensingnon-integrity of the wall.

17. The apparatus according to claim 16 including a mask confronting theradiation-transmissive wall comprising parallel louvers movable betweenradiation transmissive open positions and radiation opaque closedpositions, and including means responsive to the movement of articleswithin the second chamber and adapted to affect movement of the louversto the closed on-w e the e entgfa ticl cease 18. Apparatus forirradiating moving objects with infrared radiation comprising:

a combustion chamber having an upper wall, a flexible, gas-tight,infrared radiation-transmissive lower wall, and side walls, thecombustion chamber having an exhaust aperture positioned to drawcombustion product gases from the chamber and hav- ,ing an inletaperture permitting entry of air into the chamber;

a fuel-fired source of infrared radiation positioned within thecombustion chamber and spaced from the radiation-transmissive lowerwall;

a conveyor adapted to convey an article beneath theradiation-transmissive lower wall for exposure of the article toinfrared radiation;

an enclosure housing the conveyor, the radiationtransmissive lower wallof the combustion chamber forming an upper wall of the conveyorenclosure, the enclosure having openings permitting the flow of airtherethrough in cooling proximity to the radiation-transmissive lowerwall; and

an exhaust stack communicating with the exhaust aperture of thecombustion chamber and an opening of the conveyor enclosure tosimultaneously draw combustion product gases from the combustion chamberand cooling air from the conveyor enclosure.

19. The apparatus of claim 18 including means providing a higherpressure in the chamber than in the enclosure, whereby the flexibleradiation-transmissive lower wall is caused to balloon outwardly fromthe combustion chamber.

20. Apparatus of claim 18 including a series of louvers extending acrossthe combustion chamber adjacent the radiation-transmissive lower wall,the louvers being movable between a radiation-transmissive open positionand a radiation opaque closed position, the latter positionsubstantially preventing transmittance of radiation from the sourceexteriorly of the combustion chamber, linkage elements connected to thelouvers and adapted to move the latter between open and closedpositions, a motion sensor for sensing movement of the conveyor, and acontroller controlling movement of the linkage elements and responsiveto the sensor and adapted to affect closure of the louvers when movementof the conveyor ceases.

21. The apparatus of claim 20 including a pressure control adapted tomaintain combustion chamber pressure at a higher level than the conveyorenclosure pressure, wherein the radiation-transmissive lower wall of thechamber is sufficiently flexible as to balloon out slightly exteriorlyof the chamber in response to the pressure differential between thechamber and the enclosure, and including an integrity sensor having asensing finger touching said outwardly ballooned radiationtransmissivewall and adapted to sense the loss of integrity thereof, and a fuelcontroller responsive to the integrity sensor andadapted to shut off thesupply of fuel to the infrared radiation source in response to thesensing of non-integrity of the radiation-transmissive lower wall of thechamber.

1. Apparatus for safely emitting infrared radiation comprising a sourceof infrared radiation, an infrared radiation-transmissive, flexible wallsoftenable at a temperature below 1,000* F. and having a surfaceconfronting the radiation source but spaced therefrom, means fortransporting a coolant across the opposed surface of the wall to coolthe latter, and means preventing access of the coolant to the radiationsource.
 2. The apparatus of claim 1 wherein the radiation source isfuel-fired.
 3. Apparatus for safely emitting infrared radiationcomprising a first chamber, a source of infrared radiation enclosed inthe first chamber, a second chamber adjacent the first chamber anddesposed in radiation-receiving position with respect to the infraredradiation source, an infrared radiation-transmissive flexible wallsoftenable at a temperature below 1,000* F. and having one surfaceconfronting the radiation source and an opposed surface confronting thesecond chamber, a coolant, and means for transporting the coolant acrossthe opposed surface of the wall to cool the wall.
 4. The apparatus ofclaim 3 wherein the coolant includes an article adapted to be heatedwithin the second chamber by absorption of infrared radiation.
 5. Theapparatus of claim 3 including means for moving an article within thesecond chamber in a path permitting confrontation of the article withinfrared radiation emitted from the infrared radiation source.
 6. Theapparatus of claim 3 wherein the source of infrared radiation isfuel-fired, and including means for exhausting combustion product gasesfrom the first chamber.
 7. The apparatus of claim 3 wherein the infraredradiation-transmissive wall forms a gas-tight wall of the first chamberconfronting the second chamber.
 8. Apparatus for safely emittinginfrared radiation comprising a first chamber, a source of infraredradiation enclosed in the first chamber, a second chamber adjacent thefirst chamber and disposed in radiation-receiving position with respectto the infrared radiation source, an infrared radiation-transmissivegas-tight wall having one surface confronting the radiation source andan opposed surface confronting the second chamber, a coolant, means fortransporting the coolant across the opposed surface of the wall, and asensor for sensing the integrity of the infrared transmissive wall, thesensor including a controller responsive to the sensor and adapted todeactivate the infrared radiation source when non-integrity of the wallis sensed by the sensor.
 9. The apparatus of claim 8 wherein theinfrared transmissive wall forms a common wall of the first and secondchambers.
 10. Apparatus for safely emitting infrared radiationcomprising a first chamber, a source of infrared radiation enclosed inthe first chamber, a second chamber adjacent the first chamber anddisposed in radiation-receiving position with respect to the infraredradiation source, means for moving an article within the second chamberin a path permitting confrontation of the article with infraredradiation emitted from the source, an infrared radiation-transmissivewall having one surface confronting the radiation source and an opposedsurface confronting the second chamber, a coolant, means fortransportinG the coolant across the opposed surface of the wall, a maskconfronting the wall and having an infrared radiation-transmissive openposition and an infrared radiation opaque closed position, and includingmeans responsive to the movement of an article within the second chamberand adapted to affect closure of the mask when the movement of thearticle ceases.
 11. Apparatus for safely emitting infrared radiationcomprising a first chamber, a fuel-fired source of infrared radiationenclosed in the first chamber, a second chamber adjacent the firstchamber and disposed in radiation-receiving position with respect to theinfrared radiation source, means for moving an article within the secondchamber in a path permitting confrontation of the article with infraredradiation emitted from the source, an infrared radiation-transmissivewall having one surface confronting the radiation source and an opposedsurface confronting the second chamber, a coolant, means fortransporting the coolant across the opposed surface of the wall to coolthe wall, and an exhaust stack communicating with the first and secondchambers for exhausting combustion product gases and coolantsimultaneously from the respective chambers.
 12. The apparatus accordingto claim 5 including an infrared radiation reflector in the secondchamber and positioned to receive infrared radiation emitted from theinfrared source and to reflect the same against a portion of the articlenot confronting the infrared source.
 13. Apparatus for safelyirradiating an article with infrared radiation comprising: a fuel-firedsource of infrared radiation; a combustion chamber housing the infraredradiation source and having a gas-tight, infrared radiation-transmissiveflexible wall softenable at a temperature below 1,000* F. and spacedlyconfronting the infrared radiation source, the combustion chamberfurther having an exhaust aperture permitting combustion product gasesto be exhausted from the chamber; a conveyor for transporting an articleexteriorly of the infrared radiation-transmissive wall and in the pathof infrared radiation emitted therethrough; an enclosure housing thearticle during movement thereof in the path of the infrared radiation;and means for transporting a coolant exteriorly of, but in coolingrelationship to, the radiation-transmissive wall to cool the same. 14.The apparatus of claim 13 wherein the article enclosure is positionedbeneath the combustion chamber and wherein the radiation-transmissivewall of the chamber forms an upper wall of the article enclosure. 15.Apparatus for safely irradiating an article with infrared radiationcomprising: a fuel-fired source of infrared radiation; a combustionchamber housing the infrared radiation source and having a gas-tight,infrared radiation-transmissive lower wall spacedly confronting theinfrared radiation source and having an exhaust aperture for exhaustionof combustion product gases; a conveyor for transporting an articleexteriorly of the infrared radiation-transmissive wall and in the pathof radiation emitted through the wall; an enclosure housing the articleduring movement of the latter in the path of the infrared radiation,said infrared radiation-transmissive lower wall of the combustionchamber forming an upper wall of the article enclosure; a gaseouscoolant; and means for transporting the coolant comprising an exhauststack communicating with the combustion chamber and with the articleenclosure and adapted to simultaneously draw combustion product gasesfrom the chamber and coolant gas from the enclosure, and to exhaust thesame.
 16. The apparatus of claim 15 including a sensor for sensing theintegrity of the radiation-transmissive wall and adapted to halt fuelflow to the infrared radiation source in response to sensingnon-integrity of the wall.
 17. The apparatus according to claim 16including a mask confronting the radiation-transmissive wall comprisingpArallel louvers movable between radiation transmissive open positionsand radiation opaque closed positions, and including means responsive tothe movement of articles within the second chamber and adapted to affectmovement of the louvers to the closed position when the movement ofarticles cases.
 18. Apparatus for irradiating moving objects withinfrared radiation comprising: a combustion chamber having an upperwall, a flexible, gas-tight, infrared radiation-transmissive lower wall,and side walls, the combustion chamber having an exhaust aperturepositioned to draw combustion product gases from the chamber and havingan inlet aperture permitting entry of air into the chamber; a fuel-firedsource of infrared radiation positioned within the combustion chamberand spaced from the radiation-transmissive lower wall; a conveyoradapted to convey an article beneath the radiation-transmissive lowerwall for exposure of the article to infrared radiation; an enclosurehousing the conveyor, the radiation-transmissive lower wall of thecombustion chamber forming an upper wall of the conveyor enclosure, theenclosure having openings permitting the flow of air therethrough incooling proximity to the radiation-transmissive lower wall; and anexhaust stack communicating with the exhaust aperture of the combustionchamber and an opening of the conveyor enclosure to simultaneously drawcombustion product gases from the combustion chamber and cooling airfrom the conveyor enclosure.
 19. The apparatus of claim 18 includingmeans providing a higher pressure in the chamber than in the enclosure,whereby the flexible radiation-transmissive lower wall is caused toballoon outwardly from the combustion chamber.
 20. Apparatus of claim 18including a series of louvers extending across the combustion chamberadjacent the radiation-transmissive lower wall, the louvers beingmovable between a radiation-transmissive open position and a radiationopaque closed position, the latter position substantially preventingtransmittance of radiation from the source exteriorly of the combustionchamber, linkage elements connected to the louvers and adapted to movethe latter between open and closed positions, a motion sensor forsensing movement of the conveyor, and a controller controlling movementof the linkage elements and responsive to the sensor and adapted toaffect closure of the louvers when movement of the conveyor ceases. 21.The apparatus of claim 20 including a pressure control adapted tomaintain combustion chamber pressure at a higher level than the conveyorenclosure pressure, wherein the radiation-transmissive lower wall of thechamber is sufficiently flexible as to balloon out slightly exteriorlyof the chamber in response to the pressure differential between thechamber and the enclosure, and including an integrity sensor having asensing finger touching said outwardly ballooned radiation-transmissivewall and adapted to sense the loss of integrity thereof, and a fuelcontroller responsive to the integrity sensor and adapted to shut offthe supply of fuel to the infrared radiation source in response to thesensing of non-integrity of the radiation-transmissive lower wall of thechamber.